The invention pertains to an applicator for applying a fluid to a surface, comprising a frame, an applicator roller, such as an cylindrical brush, rotatably mounted in the frame, a fluid pick-up roller rotatably mounted in the frame, the pick-up roller being positioned beneath and parallel or substantially parallel to the applicator roller and in contact or near contact with the applicator roller, and a reservoir positioned beneath the pick-up roller.
Such applicators, usually denoted as non-contact thin film (NCTF) applicators, are known in the art, e.g. from U.S. Pat. No. 5,314,119, which describes an apparatus for applying a fluid to a moving web or sheet. A pick-up roller rotates within a supply pan and picks up a quantity of fluid on its surface. The fluid is subsequently transferred to a brush roller which is disposed adjacent to and in conjunction with the pick-up roller. The brush roller consists of a rotating cylinder or core with a large number of bristles extending radially outwardly therefrom and of such a length that the tips of the bristles impinge against the surface of the pick-up roller and pick-up a quantity of fluid. The bristles are twisted or bent and, after passing the centerline between the pick-up roller and the brush roller, the bristles snap forwardly and flick the fluid from the tips of the bristles away from the brush roller and against the said moving web or sheet.
Instead of using the pick-up roller for accomplishing this xe2x80x9cflicking actionxe2x80x9d, some applicators comprises an additional plate, sometimes denoted as flicker plate, mounted against the cylindrical brush, i.e. the distance between one of the edges of the plate and the rotational axis of the brush is smaller than the radius of the brush. Upon rotation, the brush picks up liquid from a reservoir via the pick-up roller and the flicker plate mounted against the brush causes the bristles in the brush the bent and, subsequently, flick the fluid away from the bristles thus generating a mist of droplets or particles of the fluid directed primarily in a direction substantially tangential to the brush at the point of contact of the flicker plate with the brush. The mist can be directed towards a surface to which the fluid is to be applied.
In many applications of such applicators, for example in those application where the fluid is relatively expensive, it is important to improve control of the dosage of the fluid and to enhance the uniformity of the distribution of the fluid.
Thus the invention aims to provide an applicator of the above-mentioned type wherein the control of the delivery of the fluid is improved.
To this end, the applicator according to the invention is characterised in that it further comprises a skimmer, which is located parallel or substantially parallel to at least part, preferably a substantial part or all of the pick-up roller.
It appeared that by skimming excess fluid from the pick-up roller, the said delivery of the fluid by the applicator can be controlled more effectively.
The applicator is further improved if the skimmer is pressed against the pick-up roller. The applied pressure should preferably be such that the thickness of the film of fluid on the pick-up roller remains substantially constant. In a preferred embodiment, the skimmer comprises two or more protrusions on the side facing the pick-up roller, which serve as spacers between the pick-up roller and the skimmer. Thus, control of the thickness of the film on the pick-up roller is further enhanced. The skimmer is preferably made of a plate-like and/or resilient material.
It is further preferred that the shape of the inner wall of the reservoir is adapted to the circumference over the pick-up roller so as to reduce the minimum volume of fluid required for operating the applicator. This embodiment is especially advantage if the applicator is used intermittently, since a reduced volume of fluid inherently results in a reduced risk of encrustation of the fluid contained in the reservoir.
The invention further pertains to a method of applying a fluid to a surface, such as a conveyor belt, floor, wall, or the like, by means of the applicator described supra and to the use of the said applicator for the application of a lubricant to the surface of a conveyor belt or for the maintenance, e.g. by applying a polish or a polish remover, of floors and the like.